Fiddle loop table slot interface and impl in hope of freeing slots over time.

js/src/jscntxt.h

@@ -126,6 +126,7 @@ struct JSThread {
     /* Property cache for faster call/get/set invocation. */
     JSPropertyCache     propertyCache;
 
+    /* Trace-tree recorder/interpreter state. */
     JSTraceMonitor      traceMonitor;
 };
 
@@ -410,7 +411,7 @@ struct JSRuntime {
      * loop table that tracks loop statistics is per-thread in a multi-threaded
      * environment.
      */
-    uint32              loopTableIndexGen;
+    uint32              loopTableSlotGen;
     
     /*
      * Object shape (property cache structural type) identifier generator.

js/src/jsinterp.cpp

@@ -2801,14 +2801,14 @@ JS_INTERPRET(JSContext *cx)
 
           BEGIN_CASE(JSOP_HEADER)
           {
-            uint32 index = GET_UINT24(regs.pc);
-            JS_ASSERT(index < rt->loopTableIndexGen);
+            slot = GET_UINT24(regs.pc);
+            JS_ASSERT(slot < rt->loopTableSlotGen);
 
             JSTraceMonitor *tm = &JS_TRACE_MONITOR(cx);
-            if (index >= tm->loopTableSize && !js_GrowLoopTable(cx, index))
+            if (slot >= tm->loopTableSize && !js_GrowLoopTable(cx, slot))
                 goto error;
 
-            vp = &JS_TRACE_MONITOR(cx).loopTable[index];
+            vp = &JS_TRACE_MONITOR(cx).loopTable[slot];
             rval = *vp;
             if (JSVAL_IS_INT(rval)) {
                 /*

js/src/jsscript.cpp

@@ -535,17 +535,19 @@ js_XDRScript(JSXDRState *xdr, JSScript **scriptp, JSBool *hasMagic)
     if (!ok)
         goto error;
 
-    jsbytecode *pc = code;
-    jsbytecode *end = pc + length;
-    while (pc < end) {
+    if (script->loopHeaders) {
         /* Assign a new loop table slot for every JSOP_HEADER opcode. */
-        if ((JSOp)*pc == JSOP_HEADER) {
-            uint32 slot = js_AllocateLoopTableSlot(cx->runtime);
-            SET_UINT24(pc, slot);
+        jsbytecode *pc = code;
+        jsbytecode *end = pc + length;
+        while (pc < end) {
+            if ((JSOp)*pc == JSOP_HEADER) {
+                uint32 slot = js_AllocateLoopTableSlot(cx->runtime);
+                SET_UINT24(pc, slot);
+            }
+            pc += js_OpLength(pc);
         }
-        pc += js_OpLength(pc);
     }
-    
+
     if (!JS_XDRBytes(xdr, (char *)notes, nsrcnotes * sizeof(jssrcnote)) ||
         !JS_XDRCStringOrNull(xdr, (char **)&script->filename) ||
         !JS_XDRUint32(xdr, &lineno) ||
@@ -1572,6 +1574,17 @@ js_DestroyScript(JSContext *cx, JSScript *script)
         js_FlushPropertyCacheForScript(cx, script);
     }
 
+    if (script->loopHeaders) {
+        /* Free the loop table slot for every JSOP_HEADER opcode. */
+        jsbytecode *pc = script->code;
+        jsbytecode *end = pc + script->length;
+        while (pc < end) {
+            if ((JSOp)*pc == JSOP_HEADER)
+                js_FreeLoopTableSlot(cx->runtime, GET_UINT24(pc));
+            pc += js_OpLength(pc);
+        }
+    }
+
     JS_free(cx, script);
 }
 

js/src/jstracer.cpp

@@ -47,7 +47,15 @@ js_InitTracer(JSRuntime *rt)
 }
 
 uint32
-js_AllocateLoopTableSlot(JSContext *cx)
+js_AllocateLoopTableSlot(JSRuntime *rt)
+{
+    uint32 slot = JS_ATOMIC_INCREMENT(&rt->loopTableSlotGen);
+    JS_ASSERT(slot != 0);
+    return slot - 1;
+}
+
+void
+js_FreeLoopTableSlot(JSRuntime *rt, uint32 slot)
 {
 }
 

js/src/jstracer.h

@@ -55,7 +55,7 @@
  * that loop.
  */
 struct JSTraceMonitor {
-    jsval              *loopTable;
+    jsval               *loopTable;
     uint32              loopTableSize;
 };
 
@@ -63,6 +63,7 @@ struct JSTraceMonitor {
 
 JSBool js_InitTracer(JSRuntime *rt);
 uint32 js_AllocateLoopTableSlot(JSRuntime *rt);
+void   js_FreeLoopTableSlot(JSRuntime *rt, uint32 slot);
 JSBool js_GrowLoopTable(JSContext *cx, uint32 index);
 
 #endif /* jstracer_h___ */